As a machining system, a system which has, attached to a contact surface to a tool holder at a lower end portion of a main spindle of a machine tool, a plurality of strain gauges and an output circuit for outputting detection results of the plurality of strain gauges outside, and which detects presence/absence of chips or foreign substances between the contact surface and the tool holder based on output values of the output circuit is known (for example, see PTL 1).